The present invention relates to a process for adapting the mechanical tolerances of a transmitter wheel.
More particularly, it relates to a process for adapting mechanical tolerances of a transmitter wheel with a number of approximately equidistant markings sensed by a pickup which supplies a pulse train whose time interval is measured and stored.
To detect a determined position of a shaft, e.g. the crankshaft or the camshaft of an internal combustion engine, it is known to fasten a transmitter disk having markings on its surface on the respective shaft and to sense the markings with a stationary pickup. The markings passing by the pickup, e.g. an inductive pickup, induce voltage pulses which are processed in a subsequent evaluating circuit or in a subsequent control device, the rate of rotation of the shaft being calculated from the time intervals between the voltage pulses.
A device which determines the rate of rotation and angular position of the shaft in this way is known e.g. from EP 0 188 433. A transmitter wheel with a plurality of angle marks is sensed and the obtained voltage is converted into a square-wave voltage. Information on the rate of rotation is obtained from the time intervals between identical angle mark flanks. This known device has the disadvantage either that the angle marks must be executed very exactly so that the intervals between identical angle mark flanks are very precise, or that the rate of rotation can only be determined in an inexact manner.
In the first case, a very expensive and cost-intensive production is required. In the second case, the measurement of the rate of rotation is so inexact that it cannot be used for modern internal combustion engines.
A method and a device for measuring an angle is known from DE-OS 30 18 496 in which a transmitter wheel connected with a rotating shaft and having a plurality of markings is sensed by a pickup. To increase accuracy, the intervals between the individual angle marks are first measured out in a calibrating run; these measured values are then stored and included in a subsequent evaluating process for measuring an angle.
However, the known device and process do not show that it is possible to determine the rate of rotation of the shaft exactly from the time interval between identical angle mark flanks. Also, the known device and the known process have the disadvantage that a calibrating run must be carried out prior to operation and a checking of or adaptation to changed parameters, if required, can no longer be effected during operation.